Golf clubs are typically divided into three main classes--the putters, irons and woods. The woods are generally used to hit the golf ball a long distance and the woods are traditionally constructed from wood, such as persimmon. Today, however, many woods are constructed from metal, which are generally referred to as metal woods. Metal woods allow the weight of the club head to be balanced and weight distributed around the periphery of the club head, which allows the location and size of the sweet spot of the club head to be adjusted.
A conventional metal wood is shown in U.S. Pat. No. 4,432,549 issued to Zebelean which discloses a metal driver that is cast in two parts. The first part or body includes a face plate, top crown, and sides which surround a large opening; and the second part includes a sole plate or bottom surface which is configured to fit into the large opening in the first part of the club head. After casting, the sole plate is welded to the body to form the golf club head of the metal driver. This golf club head, however, is unsatisfactory because it includes two components that must be welded together, which involves a significant amount of time and increases cost of the club head. Additionally, the lie, loft and face angle of the club head often undesirably changes because the independently formed components do not always mate in an identical manner, and the sole plate is not always welded to the body at the same angle. Thus, significant resources must be used to test and eliminate defects that occur because the sole plate and the body are not always joined at the same manner, which further increases the complexity of the manufacturing process.
Conventional metal woods which require welding the sole plate to the body are unsatisfactory because not all welds are identical. For example, differences in penetration and sealing of a weld affect the strength and structural integrity of the club head, which changes the characteristics of the club head. Welding also undesirably increases the weight and the thickness of the club head, and the differently sized welds cause an unequal weight distribution in a club head. This added weight is disadvantageous because a light-weight club head is important, and the weight is desirably positioned only in specific locations. Additionally, welding not only introduces variables during the manufacture of a single club head, it also causes variation between different club heads. Further, pieces of the weld inside the club head may break off during play. These pieces, which are located inside the sealed club head, rattle every time the club is used. The annoying rattle requires additional time, effort, money and materials to correct.
Conventional club heads are finished with a large degree of care to create the desired appearance and esthetics. For example, golf club heads are often subjected to the expensive and time consuming steps of grinding, sanding, sand blasting, polishing, tumbling and painting to finish the club head. Conventional club heads require that these steps be completed after the components are welded together because the high temperature welding will destroy or mar a finished club head. Disadvantageously, it is difficult to modify or customize the club head after it is welded together. For example, the Zebelean patent discloses filling the hollow club head with a hardening material, such as polyurethane. The Zebelean patent explains that, after the sole plate is welded to the body and the club head is finished, an opening is drilled through the center of the sole of the club head to insert the hardening material. Various types of plugging screws are used to close the opening. This golf club head is unsatisfactory because drilling the opening, filling the club head with the hardening material and sealing the opening often damages or mars the polished surface of the club head. Further, the plugging screw alters the weight and balance of the club head.
Another conventional golf club head is shown in U.S. Pat. No. 4,021,047 issued to Mader which discloses a two piece metal club head held together by mechanical fasteners. The Mader patent discloses a sole plate, face plate and hosel which are cast out of a unitary piece of metal. A wood or plastic cap fits along the top of the face plate and extends to the rear surface of the club head to form a crown and rear capping piece. The cap is attached by two screws which extend through the sole plate and hollow cavity of the club head. This golf club head, however, is unsatisfactory because the mechanical fasteners tended to loosen during play, add unnecessary weight to the club head and the weight is added to the club head in undesired locations.
Another conventional golf club head is shown in U.S. Pat. No. 5,292,129 issued to Long, et al. The Long patent discloses a metal golf club head which is reinforced by three ribs which extend between the internal surface of the striking face and the internal surface of the top side to reinforce both the striking face and the top side. This golf club head is unsatisfactory because the sole plate must be welded to the body of the golf club, and the reinforcement ribs are not interconnected to the sole plate. Disadvantageously, this allows sole plate to deform and buckle when striking a golf ball.
Therefore, there is a need for a golf club head without these significant disadvantages. In addition, there is a need for an improved golf club head which does not require welding or mechanical fasteners to attach the top crown or sole plate to the face plate.